linux-kernel - Re: [PATCH] drm/amdgpu: Fixup bad vram size on gmc v6 and v7

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Date: Mon, 22 Apr 2024 11:40:26 +0200
From: Christian König <christian.koenig@....com>
To: Qiang Ma <maqianga@...ontech.com>, alexander.deucher@....com,
 Xinhui.Pan@....com, airlied@...il.com, daniel@...ll.ch,
 srinivasan.shanmugam@....com, Arunpravin.PaneerSelvam@....com,
 le.ma@....com, Felix.Kuehling@....com, mukul.joshi@....com
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amdgpu: Fixup bad vram size on gmc v6 and v7

Am 22.04.24 um 07:26 schrieb Qiang Ma:
> Some boards(like Oland PRO: 0x1002:0x6613) seem to have
> garbage in the upper 16 bits of the vram size register,
> kern log as follows:
>
> [    6.000000] [drm] Detected VRAM RAM=2256537600M, BAR=256M
> [    6.007812] [drm] RAM width 64bits GDDR5
> [    6.031250] [drm] amdgpu: 2256537600M of VRAM memory ready
>
> This is obviously not true, check for this and clamp the size
> properly. Fixes boards reporting bogus amounts of vram,
> kern log as follows:
>
> [    2.789062] [drm] Probable bad vram size: 0x86800800
> [    2.789062] [drm] Detected VRAM RAM=2048M, BAR=256M
> [    2.789062] [drm] RAM width 64bits GDDR5
> [    2.789062] [drm] amdgpu: 2048M of VRAM memory ready

Well we had patches like this one here before and so far we always 
rejected them.

When the mmCONFIG_MEMSIZE register isn't properly initialized then there 
is something wrong with your hardware.

Working around that in the software driver is not going to fly.

Regards,
Christian.

> Signed-off-by: Qiang Ma <maqianga@...ontech.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c | 11 +++++++++--
>   drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c | 13 ++++++++++---
>   2 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
> index 23b478639921..3703695f7789 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
> @@ -309,8 +309,15 @@ static int gmc_v6_0_mc_init(struct amdgpu_device *adev)
>   	}
>   	adev->gmc.vram_width = numchan * chansize;
>   	/* size in MB on si */
> -	adev->gmc.mc_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
> -	adev->gmc.real_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
> +	tmp = RREG32(mmCONFIG_MEMSIZE);
> +	/* some boards may have garbage in the upper 16 bits */
> +	if (tmp & 0xffff0000) {
> +		DRM_INFO("Probable bad vram size: 0x%08x\n", tmp);
> +		if (tmp & 0xffff)
> +			tmp &= 0xffff;
> +	}
> +	adev->gmc.mc_vram_size = tmp * 1024ULL * 1024ULL;
> +	adev->gmc.real_vram_size = adev->gmc.mc_vram_size;
>   
>   	if (!(adev->flags & AMD_IS_APU)) {
>   		r = amdgpu_device_resize_fb_bar(adev);
> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> index 3da7b6a2b00d..1df1fc578ff6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> @@ -316,10 +316,10 @@ static void gmc_v7_0_mc_program(struct amdgpu_device *adev)
>   static int gmc_v7_0_mc_init(struct amdgpu_device *adev)
>   {
>   	int r;
> +	u32 tmp;
>   
>   	adev->gmc.vram_width = amdgpu_atombios_get_vram_width(adev);
>   	if (!adev->gmc.vram_width) {
> -		u32 tmp;
>   		int chansize, numchan;
>   
>   		/* Get VRAM informations */
> @@ -363,8 +363,15 @@ static int gmc_v7_0_mc_init(struct amdgpu_device *adev)
>   		adev->gmc.vram_width = numchan * chansize;
>   	}
>   	/* size in MB on si */
> -	adev->gmc.mc_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
> -	adev->gmc.real_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
> +	tmp = RREG32(mmCONFIG_MEMSIZE);
> +	/* some boards may have garbage in the upper 16 bits */
> +	if (tmp & 0xffff0000) {
> +		DRM_INFO("Probable bad vram size: 0x%08x\n", tmp);
> +		if (tmp & 0xffff)
> +			tmp &= 0xffff;
> +	}
> +	adev->gmc.mc_vram_size = tmp * 1024ULL * 1024ULL;
> +	adev->gmc.real_vram_size = adev->gmc.mc_vram_size;
>   
>   	if (!(adev->flags & AMD_IS_APU)) {
>   		r = amdgpu_device_resize_fb_bar(adev);